Rock-Mantled Slopes

This chapter will consider hillslopes with gradients less than 40° that are neither active, undissected piedmonts (i.e. pediments and alluvial fans, which are dealt with in Chapters 13 and 14) nor are developed in highly erodible, fine-grained sedimentary rocks (i.e. badlands slopes, which are treated in Chapter 9). Such hillslopes in desert (arid and semi-arid) climates are usually mantled with a thin layer of coarse debris that has either weathered out of the underlying substrate or fallen from a superincumbent cliff. The former hillslopes are herein referred to as debris slopes and the latter as talus slopes. In this chapter we shall first consider the processes acting on these rock-mantled slopes and then consider the forms they produce. These processes are not only important in terms of understanding hillslope form but because they give rise to a variety of hydrologic and geomorphic phenomena such as flash flooding, extreme soil erosion, and hazardous debris flows.